Main characteristics of 22 methodological research projects following studies included in trial registries.

*No definite follow-up time predictable, but more than 24 months follow-up from study completion to search for full publication fulfilled.FDA: US Food and Drug Administration, GSK: Glaxo Smith Kline, ISRCTN: International Standard Randomised Controlled Trial Number, NIH: National Institutes of Health, RCT: randomised controlled trial, WHO: World Health Organisation.Main characteristics of 22 methodological research projects following studies included in trial registries.